The contents of Japanese Application No. 9-255099 to Kuganhei, filed Sep. 19, 1997, are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a security device for a vehicle and, more particularly, to a security device for a vehicle that releases the security of a vehicle control unit such as a power train control unit loaded on the vehicle with respect only to an authorized user such as an owner of the vehicle by the use of the vehicle control unit and the user side key unit.
2. Description of the Related Art
As a security device for a vehicle, there can be cited the one that is concerned with a theft prevention device (immobilizer) for a vehicle that has a construction of releasing the security of the vehicle control unit with respect only to an authorized user such as an owner of the vehicle and permitting the use of the vehicle, the one that is concerned with a diagnosis device for a vehicle that has a construction of releasing the security of the vehicle control unit with respect only to an authorized user such as a manufacturer of the vehicle and permitting the read-in of vehicle control data of the vehicle that is secret data, and the one that is concerned with a reprogramming tool for a vehicle control microcomputer of the vehicle that releases the security of the vehicle control unit with respect only to an authorized user such as a manufacturer of the vehicle and a supplier who has made a contract with such a manufacturer so as to permits the supplier to rewrite a vehicle control program of the vehicle.
Japanese Patent Application Laid-Open No. 7-309208 discloses a technique of constructing a security device for a vehicle by the use of a vehicle control unit having an encoding algorithm and a user side key unit having the same encoding algorithm.
Specifically, such vehicle control unit generates a seed that is a kind of random number, transmits the seed to the user side key unit, and encodes the seed by the use of a predetermined encoding algorithm to thereafter generate an authentication key.
On the other hand, the user side key unit receives the seed transmitted from the vehicle control unit, encode the seed by the use of the same encoding algorithm as that used by the vehicle control unit to thereby generate a key, and transmit the thus-generated key to the vehicle control unit.
Further, in the vehicle control unit comparison is made between an authentication key generated thereby and the key transmitted from the user side key unit. When the both key coincide with each other, the security of the vehicle control unit is released.
By such a constructing, the security of the vehicle control unit is released with respect only to a proper owner of the user side key unit.
However, in the above-described security device for the vehicle, in spite of the fact that both the authentication key generated by the vehicle control unit and the key generated by the user side key unit are generated by being encoded using the seed, no concrete disclosure is made of a method of generating such a seed that is an object to be encoded.
For example, if the seed that is generated has a level of regularity, it is considered that the possibility that the authentication key and the key will coincide with each other becomes high even if such a seed is fully encoded. This becomes an obstacle to realizing a high level of security performance in the security device for the vehicle.
An object of the present invention is to provide a security device for a vehicle that has a high level of security performance by reliably generating the regularity-decreased seed in a simple and convenient manner so that this seed can be suitably used in order to generate a key by encoding this seed.
Namely, the security device for the vehicle according to the present invention is so constructed as to generate the seed used for generating the authentication key (for example, the key becoming a reference for deciding the justness of a person trying to access the vehicle) and the key (for example, the key reflecting the information on the justness of the key) by this seed being encoded, from the vehicle control data each of that has a value that is different each time when the vehicle control data is read-in at an appropriate timing during operation of the constituent elements of the vehicle.
By such a construction, the seed is reliably generated from the vehicle control data concerning the constituent elements of the vehicle that during the operation of the vehicle are always kept in some or other state of operation.
Further, since such a vehicle control data itself changes momentarily in correspondence with the state of operation of the constituent elements of the vehicle, the seed that is generated exhibits no regularity and has also a very good nature regarded as like a random number.
More concretely, the security device for the vehicle according to the present invention has a first unit that generates an authentication key by encoding the seed in accordance with a predetermined algorithm and a second unit that generates a key by encoding the seed in accordance with the same algorithm as the above-described predetermined algorithm that is used when the first unit generates the authentication key.
Here, the seed is generated according to the vehicle control data.
It is to be noted that even when the vehicle is out of operation, it is possible that the seed is stored in each of the first unit and second unit on needs.
Then, when trying to operate the vehicle, comparison is made between the key generated by the second unit held by the user and the authentication key generated by the first unit that is loaded on the vehicle and, when these two keys coincides with each other, the security on the vehicle is released to thereby operate the vehicle and enable the running thereof.
Accordingly, by making collation between the authentication key and key that is encoded by the use of the seed exhibiting a very good level of random number nature, a high level of security of the vehicle is exhibited.
Further, specifically, the first unit is a vehicle control unit and this first unit comprises a reading portion that reads in a vehicle control data, a seed generating portion that generates a seed according to the vehicle control data read in by the reading portion, a transmitting portion that transmits the seed to a second unit, an authentication key generating portion that generates an authentication key by encoding the seed in accordance with a predetermined algorithm, a key receiving portion that receives a key from the second unit, and a correspondence deciding portion that compares the key received by the key receiving portion and the authentication key generated in the authentication key generating portion and, when these key coincides with each other, releases the security on the vehicle.
In this way, by an integrated construction of from the reading portion to the correspondence deciding portion, it is possible to generate a seed and thereby determine the coincidence between the key and authentication key by a compact construction simple to use.
Here, the second unit is a user side key unit and this second unit comprises a seed receiving portion that receives the seed transmitted from the transmitting portion of the vehicle control unit, a key generating portion that generates the key by encoding the seed received by the seed receiving portion in accordance with the same algorithm as the predetermined algorithm that is used in the authentication key generating portion of the vehicle control unit, and a key transmitting portion that transmits the key generated in the key generating portion to the key receiving portion of the vehicle control unit.
In this way, through an integrated construction of from the receiving portion to the key transmitting portion, it is possible to generate the key by the compact construction simple to use and transmit it to the vehicle control unit.
Also, it is preferable that the reading portion of the vehicle control unit reads in a plurality of vehicle control data and the seed generating portion generates the seed according to the plurality of vehicle control data read in by the vehicle data reading portion because this enhances the random number-like nature of the seed and as a result enhances the security level of the vehicle.
Here, specifically, the seed generating portion adds up the seed generated at the time of the previous vehicle operation and the plurality of vehicle control data that is read in by the reading portion to thereby newly generate a seed having substantially no regularity on a reliable basis.
Also, the vehicle control unit is a power train control unit and the vehicle control data that is read into the reading portion is at least one of an engine revolutions number, sucked air amount, throttle opening and water temperature.
Here, the power train control unit means a control unit that can control an engine control unit singly, or a transmission control unit singly, or both of the engine control unit and the transmission control unit synthetically.
According to such a construction, the security device for the vehicle according to the present invention has a simple and convenient construction that is integral with the power train control unit. Further, because the engine control data such as an engine revolutions number are the values that irregularly change and reliably exist, these data are suitable for use in the generation of a seed.
Also, the vehicle control unit is a power train control unit and the vehicle control data that is read into the reading portion may include the counted time value of a so-called xe2x80x9cfree run timerxe2x80x9d that is counted until the ignition switch is changed over to xe2x80x9coffxe2x80x9d after this switch was made xe2x80x9conxe2x80x9d. Therefore, even if the ignition key has been operated repeatedly, the level of security becomes high. It is to be noted that such counted time value corresponds to the xe2x80x9conxe2x80x9d time duration of the ignition switch and therefore shall be a kind of control data of the vehicle.
Also, the vehicle control unit is a power train control unit and the vehicle control data that is read into the vehicle data reading portion may include an amount of fuel injection and/or ignition energy. Such engine control output data can be suitably used as in the case of the engine control input data such as an engine revolutions number.
Meanwhile, the security device for the vehicle according to the present invention is possibly constructed as an immobilizer that compares the key generated by the second unit and the authentication key generated by the first unit and, when these data coincides with each other, brings the vehicle to an operable state.
Also, the security device for the vehicle according to the present invention is possibly constructed as a diagnosis device for the vehicle that compares the key generated by the second unit and the authentication key generated by the first unit and, when these data coincides with each other, brings the vehicle to a state where the vehicle control data is readable.
Also, the security device for the vehicle according to the present invention is possibly constructed as a reprogramming tool that compares the key generated by the second unit and the authentication key generated by the first unit and, when these data coincides with each other, brings the vehicle to a state where the vehicle control program is rewritable.
Further, in other words, the security device for the vehicle according to the present invention can be said as having a construction that comprises seed generating means that generates a seed according to the vehicle control data, authentication key generating means that generates an authentication key by encoding the seed in accordance with a predetermined algorithm, key generating means that encodes the seed in accordance with the same algorithm as the predetermined algorithm that is used when the first authentication key generating means generates the authentication key to thereby generate a key, and correspondence deciding means that compares the key and the authentication key to thereby decide whether these data are in coincidence with each other, whereby when the correspondence deciding means decides that the key and the authentication key are in coincidence with each other, the security that concerns the vehicle is released.